Light emitting device having surface-modified quantum dot luminophores

ABSTRACT

Exemplary embodiments of the present invention relate to a light emitting device including a light emitting diode and a surface-modified luminophore. The surface-modified luminophore includes a quantum dot luminophore and a fluorinated coating arranged on the quantum dot luminophore.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.13/209,733, filed on Aug. 15, 2011, and claims priority from and thebenefit of German Patent Application No. 10 2010 034 322.6, filed onAug. 14, 2010, and Korean Patent Application No. 10-2010-0137026, filedon Dec. 28, 2010, which are all hereby incorporated by reference for allpurposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Exemplary embodiments of the present invention relate to light emittingdevices having inorganic luminophores based on doped alkaline earthmetal silicate compounds and quantum dot semiconductor compounds whichare capable of converting high-energy primary radiation, i.e., forexample, ultraviolet (UV) radiation or blue light, to alonger-wavelength secondary radiation within the visible spectralregion, which can be used as radiation converters in light-emittingdevices such as color or white-light emitting light emitting diodes(LEDs). Exemplary embodiments of the present invention also relate tolight emitting devices having silicatic inorganic luminophores orquantum dot luminophores which may have improved stability to airhumidity and other environmental factors, and increased operationallifetime.

2. Discussion of the Background

Luminophores may be used in light sources, such as LEDs that emitcolored or white light. In an LED, luminophores, which may be used incombination with other luminophores, are used to convert ultraviolet orblue primary radiation emitted from an LED into longer wavelengthsecondary radiation, in particular, white light.

Alkaline earth metal silicate luminophores, which include theeuropium-doped alkaline earth metal orthosilicates, the correspondingoxyorthosilicates and the disilicates of the Ba(Sr)3MgSi2O8:Eu form,have been known for some time. An overview of the classification of thealkaline earth metal silicate compounds is documented byHollemann-Wiberg, “Lehrbuch der Anorganischen Chemie” InorganicChemistry, 102 edition, (Walter de Gruyter & Co., Berlin, 2007). Thepreparation and the essential luminescence properties thereof have beendescribed in detail in various patents and publications, for example:U.S. Pat. No. 6,489,716, issued to Tews, et al.; EP Appl. Pub. No.0550937, applied for by Ouwerkerk, et al.; EP Appl. Pub. No. 0877070,applied for by Hase, et al.; and by W. M. Yen et al., “PhosphorHandbook”, 2nd Ed., CRC Press (2007). These publications indicate thatsuch luminophores have high quantum and radiation yields for theconversion of high-energy radiation to visible light, and numerousrepresentatives of this luminophore class, due to these properties, maybe used in products for lighting, illumination, and display technology.

However, the luminophores based on the alkaline earth metal silicatesalso have various disadvantageous properties. Some of the disadvantagesinclude a comparatively low radiation stability and high sensitivity ofthe luminophores to water, air humidity, and other environmentalfactors. The sensitivity depends on the particular composition of theluminophore, structural conditions, and the nature of activator ions ofthe luminophores. For some of the current applications ofwavelength-conversion luminophores, these properties may be problematic.In view of the high lifetime demands, this may apply to LEDapplications. One known solution is to use suitable technologies andmaterials to generate (on the surface of pulverulent inorganicluminophores) barrier layers for reducing the influence of water vapour.

These processes may include encapsulation with organic polymers, coatingwith nanoscale oxides such as SiO2 or Al2O3, or chemical vapourdeposition (CVD) of such oxides. However, in relation to silicaticluminophores, the protection achievable may be insufficient to improvethe lifetime of corresponding LED lamps to the desired degree.Furthermore, in the case of coated luminophores, it may be necessary toaccept losses in brightness, shifts in the color location, and otherquality losses. Processes for microencapsulation of the luminophoreparticles by means of gas phase processes may be inconvenient andcostly.

Quantum dots also can be used as luminophores and their wavelengthsbecome shorter as their sizes become smaller. Quantum dots are veryreactive due to their small size, and thus, quantum dots have also acomparatively low radiation stability and high sensitivity to water, airhumidity, and other environmental factors.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention provide light emittingdevices employing silicate or quantum dot luminophores that may providemoisture stability, stability to radiation and other environmentalinfluences, and improved operational lifetime.

Exemplary embodiments of the present invention also provide lightemitting devices employing luminophores that have been subjected to asurface treatment with fluorinated inorganic or organic agents.

Exemplary embodiments of the present invention also provide detectablefixing of finely dispersed fluorides or fluorine compounds on theluminophore surface or the formation of surface networks of suchcompounds which are capable of making the luminophore surfaceshydrophobic and may cure surface defects.

Additional features of the invention will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention.

An exemplary embodiment of the present invention discloses a lightemitting device including a first light emitting diode and asurface-modified luminophore configured to absorb light emitted from thefirst light emitting diode and configured to emit light having adifferent wavelength from the absorbed light, wherein thesurface-modified luminophore includes a quantum dot (QD) luminophore anda fluorinated coating arranged on the or QD luminophore.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.Additional features of the invention will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of theinvention, and together with the description serve to explain variousaspects of the invention.

FIG. 1 is a cross-sectional view of a light emitting device 100,according to an exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view of a light emitting device 200,according to an exemplary embodiment of the present invention.

FIG. 3 is a cross-sectional view of a light emitting device 300,according to an exemplary embodiment of the present invention.

FIG. 4 is a cross-sectional view of a light emitting device 400,according to an exemplary embodiment of the present invention.

FIG. 5 is a cross-sectional view of a light emitting device 500,according to an exemplary embodiment of the present invention.

FIG. 6 a is emission spectra of a reference materialSr_(2.9)Ba_(0.01)Ca_(0.05)Eu_(0.04)SiO₅, a commercial Sr₃SiO₅:Euluminophore, and oxyorthosilicate luminophores F-103, F-202, F-202T,F-320 and F-TS-600 according to exemplary embodiments of the presentinvention.

FIG. 6 b is emission spectra of reference materialSr_(0.876)Ba_(1.024)Eu_(0.1)SiO₄ and two alkaline earth metalorthosilicate luminophores F-401 and F-401TS according to exemplaryembodiments of the present invention.

FIG. 7 a is electron micrographs of non-fluorinated and fluorinatedalkaline earth metal oxyorthosilicate luminophores, showing untreatedparticles of the luminophore Sr_(2.9)Ba_(0.01)Ca_(0.05)SiO on the leftand fluorinated particles of the luminophore F-202 according to anexemplary embodiment of the present invention on the right.

FIG. 7 b includes magnified electron micrographs of the surface of theluminophore F-202 according to an exemplary embodiment of the presentinvention.

FIG. 8 includes electron micrographs of uncoated, fluorinated, andSiO₂-coated alkaline earth metal orthosilicate luminophores of the baselattice composition Sr_(0.876)Ba_(1.024)SiO₄:Eu_(0.1), showing ascanning electron micrograph of the uncoated starting material on theleft, the fluorinated luminophore surface in the middle, and aluminophore sample additionally coated with SiO₂ on the right accordingto an exemplary embodiment of the present invention.

FIG. 9 is an energy-dispersive X-ray (EDX) spectroscopic image of theluminophore F-103 with manifested fluorinated surface structureaccording to an exemplary embodiment of the present invention.

FIG. 10 is an X-ray photoelectron (XPS) spectrum of the luminophoreF-103 according to an exemplary embodiment of the present invention.

FIG. 11 is a graph showing representative fluorine XPS peaks fordifferent luminophore samples. Curve 1 relates to the mechanical mixtureof the luminophore having the compositionSr_(2.9)Ba_(0.01)Ca_(0.05)Eu_(0.04)SiO₅ with an amount of NH₄F accordingto working example A1, and curve 2 relates to the fluorine is peak ofthe fluorinated luminophore F-103 according to an exemplary embodimentof the present invention.

FIG. 12 depicts a sectional view of a surface modified quantum dotluminophore according to an exemplary embodiment of the presentinvention.

FIG. 13 depicts a sectional view of a surface modified quantum dotluminophore according to another exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The invention is described more fully hereinafter with reference to theaccompanying drawings, in which exemplary embodiments of the inventionare shown. This invention may, however, be embodied in many differentforms and should not be construed as limited to the exemplaryembodiments set forth herein. Rather, these exemplary embodiments areprovided so that this disclosure is thorough, and will fully convey thescope of the invention to those skilled in the art. In the drawings, thesize and relative sizes of layers and regions may be exaggerated forclarity. Like reference numerals in the drawings denote like elements.

It will be understood that when an element or layer is referred to asbeing “on” or “connected to” another element or layer, it can bedirectly on or directly connected to the other element or layer, orintervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on” or “directly connected to”another element or layer, there are no intervening elements or layerspresent. It will be understood that for the purposes of this disclosure,“at least one of X, Y, and Z” can be construed as X only, Y only, Zonly, or any combination of two or more items X, Y, and Z (e.g., XYZ,XYY, YZ, ZZ).

According to exemplary embodiments of the present disclosure, a lightemitting device includes a light emitting diode that emits light in theUV or visible range, and a surface-modified luminorphore disposed aroundthe light emitting diode to absorb at least a portion of light emittedfrom the light emitting diode and to emit light having a differentwavelength from the absorbed light.

On excitation with high-energy UV radiation, blue light, electron beams,X-rays or gamma rays and, depending on their specific chemicalcomposition and the nature of an activator, the luminophores accordingto exemplary embodiments of the present invention may emit visible lightand infrared radiation with high radiation yields and significantlyimproved stability to H₂O, air humidity, and other environmental factorscompared to the prior art. For this reason, they may be used inlong-life industrial products, for example in cathode ray tubes andother image-generating systems (scanning laser beam systems) in X-rayimage converters, high-performance light sources, LEDs of all colors forinterior and exterior illumination, backlighting of LCD displays, solarcells, greenhouse films, and glasses as radiation converters.

Luminophores according to exemplary embodiments of the presentinvention, including surface-modified silicate luminophores, may becharacterized in that the surface thereof has a coating of fluorinatedinorganic or organic agents for generation of hydrophobic surface sites,or of a combination of the fluorinated coating with one or more moisturebarrier layers. The moisture barrier layers may be formed usinglayer-forming materials such as at least one of the oxides MgO, Al₂O₃,Ln₂O₃ (wherein Ln═Y, La, Gd, or Lu), and SiO₂, or the correspondingprecursors, and sol-gel technologies.

Luminophores, including surface-modified silicate luminophores,according to exemplary embodiments of the present invention may includepulverulent alkaline earth metal silicate luminophores. Thesurface-modified silicate luminophores may have the general formula:

(Me1+Me2+Me3+)x.(Si,Al,B,P,V,N,C,Ge)y.(O,N)z:(A,F,S)

where A is an activator selected from the group of the lanthanoids ormanganese; F is a surface fixed and optionally cross-linked fluorine orfluorine compounds; and S characterizes an optional additional coatingwith non-fluorinated layer-forming materials. Me¹⁺ is a monovalentmetal, Me²⁺ is a divalent metal and Me³⁺ is a trivalent metal selectedfrom group III of the Periodic Table or from the lanthanoids. Some ofthe silicon may be replaced by P, Al, B, V, N, Ge, or C. Thecoefficients x, y, and z may have the following ranges: 0<x<5, 0<y<12,and 0<z<24.

According to exemplary embodiments of the present invention, which mayoptimize luminescence properties and stability performance, some of thealkaline earth metal ions in the surface-modified silicate luminophoresmay be replaced by further divalent ions, for example Mg, Zn, or, withimplementation of suitable measures for balancing the charge, monovalentor trivalent cations from the group of alkali metals or of the rareearths. Further, P, B, V, N, Ge, or C can be incorporated into an anionsublattice of the surface-modified silicate luminophores replacing someof the silicon.

According to exemplary embodiments of the present invention, thealkaline earth metal silicate luminophores may be fluorinated usingfluorine-functionalized organosilanes of the Si(OR)₃X form where R═CH₃,C₂H₅, . . . , and X=a F-functionalized organic ligand, and controlledhydrolysis and condensation may achieve the formation of a fluorinatedbarrier layer on a silicatic luminophore matrix, which may be a barrierand may also have hydrophobic properties.

The surface-modified silicate luminophores according to exemplaryembodiments of the present invention, may be characterized by thegeneral formula:

Sr_(3-x-y-z)Ca_(x)Ba_(y)SiO₅:Eu_(z),F,S

wherein 0≦x≦2, 0≦y≦2 and 0<z<0.5. The surface-modified silicateluminophores according to exemplary embodiments of the presentinvention, may also be characterized by the formula:

Sr_(3-x-y-z)Ca_(x)Ba_(y)SiO₅:Eu_(z),F,S

wherein 0≦x≦0.05, 0≦y≦0.5 and 0<z<0.25.

As discussed above, silicate luminophores are surface modified with acoating including a fluorinated coating. However, the application of thefluorinated coating is not limited on the silicate luminophores. Thefluorinated coating can also be applied to quantum dot (QD)luminophores. Semiconductor quantum dot luminophores convert high energyradiation into visible light, based on their band gap structure. Inaddition, quantum dot luminophores are very reactive due to their smallsize, and thus, quantum dots have also a comparatively low radiationstability and high sensitivity to water, air humidity, and otherenvironmental factors.

The QD luminophore may comprise a II-VI or III-V group compoundsemiconductor QD luminophore. The II-VI group compound semiconductor QDluminophore may comprise CdSe or CdS, and the III-V group compoundsemiconductor QD luminophore may comprise AlInGaP, AlInGaAs, or AlInGaN,but the invention is not limited thereto.

The light emitting device, according to the exemplary embodiments of thepresent invention, may emit white light or a desired color of lightthrough a combination of the light emitted from the light emitting diodeand the luminophore. Furthermore, other luminophores may be added to thelight emitting device to emit another desired color of light. Theluminophores may be disposed on at least one of lateral, upper, andlower sides of the light emitting diode. Further, the luminophores maybe mixed with an adhesive or a molding material, which may be disposedon the light emitting diode.

The light emitting diode and the luminophores may be combined in asingle package. According to an exemplary embodiment of the presentinvention, the light emitting device may further include another lightemitting diode in the package. The other light emitting diode may emitlight having the same wavelength as, or a different wavelength from, thelight emitted from the light emitting diode. For example, the otherlight emitting diode may emit light having a longer wavelength than anemission peak wavelength of the luminophore.

The package may include a substrate such as a printed circuit board orlead frame, on which the light emitting diode is mounted. According toone exemplary embodiment of the present invention, the package mayfurther include a reflector that reflects light emitted from the lightemitting diode. In the present exemplary embodiment, the light emittingdiode is mounted within the reflector.

The light emitting device may further include a molding member thatencapsulates the light emitting diode on the substrate. The luminophoresmay be dispersed in the molding member, but are not limited thereto. Thepackage may further include a heat sink, and the light emitting diodemay be mounted on the heat sink.

According to exemplary embodiments of the present invention, the lightemitting diode may be formed of (Al, Ga, In)N-based compoundsemiconductors. The light emitting diode may have, for example, adouble-hetero structure, a single quantum well structure, ormulti-quantum well structure, wherein a single active region is arrangedbetween an n-type semiconductor layer and a p-type semiconductor layer.

The light emitting diode may further include a plurality of lightemitting cells that are separated from each other and disposed on asingle substrate. Each of the light emitting cells may have an activeregion. The light emitting cells may be electrically connected to oneanother in series and/or in parallel, via wires. With these lightemitting cells, it is possible to provide an alternating current (AC)light emitting diode which may be directly driven by an AC power supply.Such an AC-light emitting diode may be driven without an additionalAC/DC converter, by forming a bridge rectifier and serial arrays oflight emitting cells connected to the bridge rectifier on a singlesubstrate, or by forming serial arrays of light emitting cells connectedin reverse-parallel to one another on a single substrate.

FIG. 1 is a cross-sectional view of a light emitting device 100according to an exemplary embodiment of the present invention. The lightemitting device 100 may be referred to as a chip-type package. Referringto FIG. 1, electrodes 5 may be formed on both sides of a substrate 1,and a light emitting diode 6 to emit primary light may be mounted on oneof the electrodes 5, at one side of the substrate 1. The light emittingdiode 6 may be mounted on the electrode 5 via an electrically conductiveadhesive 9, such as Ag epoxy, and may be electrically connected to theother electrode 5 via an electrically conductive wire 2. The lightemitting diode 6 emits light in the ultraviolet range or visible rangeand may be formed of gallium nitride-based compound semiconductors. Thelight emitting diode 6 may emit UV or blue light.

Luminophores 3 may be dotted on upper and side surfaces of the lightemitting diode 6. A molding member 10, for example, a thermosettingresin, encapsulates the light emitting diode 6. The luminophores 3 aredotted around the light emitting diode 6, but are not limited to anyparticular configuration. For example, the luminophores 3 may beuniformly distributed within the molding member 10. The luminophores 3absorb at least a portion of light emitted from the light emitting diode6 and emit light having a different wavelength from the absorbed light.

The light emitting diode 6 is electrically connected to an externalpower supply via the electrodes 5 and thus, may emit primary light. Theluminophores 3 absorb at least a portion of the primary light and emitsecondary light having a wavelength that is longer than that of theprimary light. As a result, the primary light and the secondary lightare mixed to form mixed light, which is emitted from the light emittingdevice 100. A desired color of light, for example white light, may berealized in this manner.

The light emitting device 100 may include one or more additional lightemitting diodes. These light emitting diodes may emit light having thesame emission peaks or different emission peaks. For example, the lightemitting device 100 may include the same or different types of lightemitting diodes, each of which can emit ultraviolet or blue light.Furthermore, the light emitting device 100 may include a light emittingdiode that can emit light having a longer wavelength than the emissionpeak wavelength of the luminophores. Such a longer wavelength lightemitting diode may be employed to improve a color rendering index of thelight emitting device 100. Moreover, the light emitting device 100 mayfurther include other luminophores in addition to the luminophores 3.Examples of the other luminophores include, but are not limited to,orthosilicate luminophores, Yttrium Aluminum Garnet (YAG) basedluminophores, and thiogallate luminophores. Accordingly, a desired colorof light may be achieved by the proper selection of the light emittingdiodes 6 and luminophores.

FIG. 2 is a cross-sectional view of a light emitting device 200,according to another exemplary embodiment of the present invention. Thelight emitting device 200 may be referred to as a top-view type package.Referring to FIG. 2, the light emitting device 200 has a similarstructure to the light emitting device 100 and further includes areflector 21 on a substrate 1. A light emitting diode 6 is mounted inthe reflector 21. The reflector 21 reflects light emitted from the lightemitting diode 6, to increase brightness within a certain viewing angle.

Luminophores 3 are disposed around the light emitting diode 6, absorb atleast a portion of the light emitted from the light emitting diode 6,and emit light having a different wavelength than the absorbed light.The luminophores 3 may be dotted on the light emitting diode 6 or may beuniformly distributed within a thermosetting resin molding member 10.

The light emitting device 200 may also include one or more additionallight emitting diodes, which emit light having the same emission peaksor different emission peaks from one another, and may further includeother luminophores in addition to the luminophores 3.

The light emitting devices 100, 200 may include substrates 1 formed of ametallic material, for example a metal printed circuit board (PCB),which exhibits good thermal conductivity. Such a substrate may easilydissipate heat from the light emitting diode 6. Further, a lead frameincluding lead terminals may be used as the substrate 1. Such a leadframe may be surrounded and supported by the molding member 10, whichencapsulates the light emitting diode 6.

In the light emitting device 200, the reflector 21 may be formed of adifferent material from the substrate 1, although is not limitedthereto. For example, the reflector 21 may be formed of the same type ofmaterial as the substrate 1. A lead frame having lead terminals may beintegrally formed with the substrate 1 and reflector 21, byinsert-molding plastics such as polyphthalamide (PPA). Then, the leadterminals may be bent to form the electrodes 5.

FIG. 3 is a cross-sectional view of a light emitting device 300,according to another exemplary embodiment of the present invention. Thelight emitting device 300 may be referred to as a light emitting diodelamp. Referring to FIG. 3, the light emitting device 300 includes a pairof lead electrodes 31, 32 and a cup portion 33 having a cup shape, at anupper end of one lead electrode 31. At least one light emitting diode 6may be mounted in the cup portion 33 via an electrically conductiveadhesive 9 and electrically connected to the other lead electrode 32 viaa conductive wire 2. When a plurality of light emitting diodes ismounted within the cup portion 33, the light emitting diodes may emitlight having the same wavelength or different wavelengths from oneanother.

Luminophores 3 are disposed around the light emitting diode 6. Theluminophores 3 absorb at least a portion of light emitted from the lightemitting diode 6 and emit light having a different wavelength from thatof the absorbed light. The luminophores 3 may be dotted on the lightemitting diode 6 in the cup portion 33, or uniformly distributed withina thermosetting resin molding member 34 formed in the cup portion 33.

A molding member 10 encapsulates the light emitting diode 6, theluminophores, and a portion of the lead electrodes 31, 32. The moldingmember 10 may be formed of, for example, epoxy or silicone. In thepresent exemplary embodiment, the light emitting device 300 includes thepair of lead electrodes 31, 32. However, the light emitting device 300may have more lead electrodes than the pair of lead electrodes 31, 32.

FIG. 4 is a cross-sectional view of a light emitting device 400,according to yet another exemplary embodiment of the present invention.The light emitting device 400 may be referred to as a high-power lightemitting diode package. Referring to FIG. 4, the light emitting device400 includes a heat sink 41 that is received in a housing 43. The heatsink 41 has a bottom surface that is exposed to outside. Lead electrodes44 are exposed within the housing 43 and extend outside through thehousing 43. At least one light emitting diode 6 may be mounted on anupper surface of the heat sink 41, via an electrically conductiveadhesive 9. The light emitting diode 6 is electrically connected to oneof the lead electrodes 44, via an electrically conductive wire 2.Furthermore, another electrically conductive wire 2 connects the otherlead electrode 44 to the heat-sink 41, such that the light emittingdiode 6 may be electrically connected to each of the two lead electrodes44.

Luminophores 3 are disposed around the light emitting diode 6, on theheat-sink 41. The luminophores 3 adsorb at least a portion of lightemitted from the light emitting diode 6 and emit light having adifferent wavelength from that of the absorbed light. The luminophores 3may be dotted on the light emitting diode 6, or uniformly distributedwithin a molding member (not shown), to cover the light emitting diode.

FIG. 5 is a cross-sectional view of a light emitting device 500,according to yet another exemplary embodiment of the present invention.Referring to FIG. 5, the light emitting device 500 includes a housing 53and a plurality of heat-sinks 51, 52 that may be joined to the housing53 and insulated from each other. Light emitting diodes 6, 7 are mountedon the heat-sinks 51, 52, via an electrically conductive adhesive. Thelight emitting diodes 6, 7 are electrically connected to lead electrodes54, via respective electrically conductive wires (not shown). The leadelectrodes 54 extend from the inside of the housing 53 to the outside.Each of the light emitting diodes 6, 7 is connected to two of the leadelectrodes 54, but more lead electrodes may be provided thereto.Luminophores 3 may be disposed around at least one of the light emittingdiodes 6 or 7, as described with reference to FIG. 4.

In the above exemplary embodiments, the light emitting diode 6 may bemounted on the substrate 1 or on the heat-sink 41, via the electricallyconductive adhesive 9, and electrically connected to the electrode orlead electrode via the electrically conductive wire 2. When the lightemitting diode 6 is a “two-bond die”, which has two electrodes on thetop side thereof, the light emitting diode 6 may be electricallyconnected to the electrodes or lead electrodes via two electricallyconductive wires, respectively. Thus, the adhesive need not beelectrically conductive.

In some exemplary embodiments, the light emitting diode 6 may be formedof an (Al, Ga, In)N-based composite semiconductor. The light emittingdiode 6 may have, for example, a double hetero-structure, single quantumwell structure, or multi-quantum well structure, which may have a singleactive region arranged between n-type and p-type semiconductor layers.

Luminophore powders used as the basis for the preparation of thesurface-modified silicate luminophores 3 according to an exemplaryembodiment of the present invention may be synthesized by multistagehigh-temperature solid-state reactions at temperatures above 1000° C.between the alkaline earth metal carbonates that may be used as thestarting material or the corresponding metal oxides and SiO₂.Additionally, mineralization additives (e.g. NH₄Cl, NH₄F, or alkalimetal or alkaline earth metal halides or halides of the trivalentmetals) may be added to the reaction mixture to promote reactivity andto control the particle size distribution of the resulting luminophores.Depending on the specific selection of the stoichiometric ratios, it maybe possible to produce the desired compositions of the doped alkalineearth metal silicate luminophores, more particularly the correspondingortho- and oxyortho-silicate luminophores.

Accordingly, the calculated amounts of the starting materials are mixedvigorously and then subjected to a multistage calcination process in aninert or reducing atmosphere within the desired temperature range. Forthe purpose of optimizing the luminophore properties, the maincalcination process may optionally also have several calcination stageswithin different temperature ranges. After the calcination process hasended, the samples are cooled to room temperature and subjected tosuitable aftertreatment processes that are directed, for example, to theelimination of flux residues, to the minimization of surface defects, orelse to the tine adjustment of the particle size distribution. Insteadof the silicon oxide, it is alternatively also possible to use siliconnitride (Si₃N₄) or other silicon-containing precursors as reactants forthe reaction with the alkaline earth metal compounds used. The synthesisof the polycrystalline luminophore powders used for the production ofexemplary embodiments of the luminophores is not restricted to thepreparation processes described above.

For the fluorination of the surfaces of the pulverulent alkaline earthmetal silicate luminophores according to the present invention,different inorganic fluorine compounds may be used such as alkali metalfluorides (e.g. LiF, NaF, KF) alkaline earth metal fluorides (MgF₂,CaF₂, SrF₂, BaF₂), AlF₃ and fluorides of the rare earths (e.g. YF₃, LaF₃or GdF₃), NH₄F and NH₄HF₂, and also other inorganic or organic fluorinecompounds (e.g. fluoride-containing amines). The materials selected aremixed with the silicatic luminophore powders, in which case aqueoussuspensions may be employed. The required proportions of thefluorinating agents added depend on the solubility of the compounds andon the reaction conditions (pH, temperature, intensity of mixing,residence time, etc.) and may be determined experimentally.

After the surface treatment has ended, the fluorinated luminophores areremoved from the suspension, and may be washed with suitable solventsand then dried at temperatures between 80° C. and 200° C. After coolingand screening, they are in a form ready for use.

For the achievement of optimal luminophore properties, depending on thespecific composition of the inventive luminophores, on the type andamount of the fluorinating agents used, and further factors, to subjectthe luminophores produced in accordance with the invention, additionallyor instead of the drying process, to a thermal aftertreatment (heattreatment) within a temperature range from 300° C. to 600° C. in areducing atmosphere. Detailed information regarding the production ofthe luminophores according to exemplary embodiments of the presentinvention is given hereinafter by several working examples.

Working Example A1

Working Example A1 describes the preparation of a luminophore providedwith a fluorinated surface layer and having the base lattice compositionSr_(2.9)Ba_(0.01)Ca_(0.05)SiO₅:Eu_(0.04) according to an exemplaryembodiment of the present invention, which is described as sample F-103together with its optical data in Table 1, and the emission spectrumthat is designated as “3” in FIG. 6 a.

Table 1 contains optical and moisture stability data ofeuropium-activated strontium oxyorthosilicate luminophore samples whichhave been treated with different amounts of NH₄F. To synthesize thecorresponding luminophore matrix, the stoichiometric amounts of SrCO₃,BaCO₃, CaCO₃, Eu₂O₃, and SiO₂ and 0.2 mol of NH₄Cl are mixed vigorouslyand then subjected, in corundum crucibles, to a 5-hour calcinationprocess at 1400° C. in an N₂/H₂ atmosphere containing 2% hydrogen. Afterthe calcination process has ended, the calcinated material ishomogenized, ground and washed with H₂O. Subsequently, 100 g of thedried and screened luminophore are introduced together with 1.1 g ofNH₄F, 200 g of glass beads and 1 liter of water into a suitable plasticvessel and mixed vigorously on a jar mill at low speed for 30 minutes.After a settling time of several minutes, the supernatant is firstdecanted and then filtered with suction through a Büchner funnel. Thisis followed by drying and screening of the end product.

Working Example A2

To prepare the luminophore containing sample F-202 according to anexemplary embodiment of the present invention, the optical data of whichare specified in Table 2 and the emission spectrum of which isdesignated as “4” in FIG. 6 a, 100 g of the luminophore matrix describedin Working Example A1 are mixed with 2.474 g of NH₄HF₂. Table 2 containsoptical and moisture stability data of europium-activated strontiumoxyorthcsilicate luminophore samples which have been treated withdifferent amounts of NH₄HF₂. In this case, the fluorinated surface layeris applied by wet-chemical precipitation by taking the mixture in 1 L ofdeionized water and 400 g of glass beads on a roll mill. Treatment forone hour is followed by the removal of the coated luminophore from thesolution and an after-treatment analogous to Working Example A1.

Working Example A3

Here, 30 g of the luminophore produced according to Working Example A2are heat treated in a corundum crucible at 400° C. in an N₂/H₂atmosphere containing 35% hydrogen for 60 minutes. After cooling, thesample F-202T, the optical data of which are specified in Table 2 andthe emission spectrum of which is designated as “5” in FIG. 6 a, ishomogenized by screening to produce an exemplary embodiment of thepresent invention.

Working Example A4

An oxyorthosilicate luminophore with a base lattice compositionSr_(2.948)Ba_(0.01)Cu_(0.002)SiO₅:Eu_(0.04) according to an exemplaryembodiment of the present invention is synthesized in the solid stateaccording to Working Example A1 and coated with an SiO₂ network usingprecursor material tetraethoxysilane (TEOS). For this purpose, 50 g ofthe luminophore are mixed with 500 mL of a solution of 1 L of ethanol,18.2 g of TEOS and 100 mL of 32% aqueous ammonia, and stirred in areaction vessel for 2 hours. Thereafter, the coated luminophore isfiltered with suction, washed with ethanol, and dried at 160° C. for 24hours.

After this preparative surface treatment, the luminophore is subjected,as in Working Example A1, to fluorination by NH₄F as the fluorinatingagent. For this purpose, 80 g of the precoated luminophore is reactedwith 1.98 g of NH₄F under the conditions of Working Example A1. Theluminophore according to the present exemplary embodiment is thusproduced, in the form of sample F-TS-600. The optical data of which aredescribed in Table 6, and the emission spectrum of which is designatedas “7” in FIG. 6 a, like the luminophore described in Working ExamplesA1, A2, and A3, and may have a significantly improved moistureresistance compared to conventional oxyorthosilicate luminophores andthe same base lattice composition as the uncoated base luminophores. Theperformance characteristics of these luminophores according to theexemplary embodiments of the present invention are compiled in Tables 1,2 and 6.

Working Example B1

For the production of the luminophore according to an exemplaryembodiment of the present invention in the form of sample F-320, a baselattice of the composition Sr_(2.9485)Ba_(0.01)Cu_(0.0015)SiO₅:Eu_(0.04)is synthesized. For this purpose, the stoichiometric amounts of SrCO₃,BaCO₃, CuO, Eu₂O₃, 65 g of SiO₂ and 0.3 mol of NH₄Cl are mixed,introduced into suitable calcining crucibles and calcined in ahigh-temperature furnace for a period of 24 hours. The calcinationprogram has two main calcination zones at 1200° C. and 1350° C. for 3hours at each temperature. During the first calcination phase,calcination is effected under forming gas with hydrogen concentration5%, and the hydrogen concentration is increased to 20% in the subsequentsecond phase of calcination.

The cooling, washing and homogenization of the matrix material arefollowed by the fluorination of the luminophore surface. To this end,the fluorinating agent used is aluminium fluoride AlF₃ instead of theNH₄F or the NH₄HF₂. For interaction with the surface of the luminophoreparticles, 1.2 g of AlF₃ are introduced into 1 L of H₂O at 60° C. andthe mixture is stirred vigorously for 1 hour. Subsequently, 100 g of theluminophore matrix synthesized are added to the suspension. The reactiontime may be 60 minutes. The coated luminophore in the form of sampleF-320 is after-treated similarly to Working Examples A1, A2, A3, and A4.The optical data are shown in Table 3, and the emission spectrum thereofis designated as “6” in FIG. 6 a. Table 3 contains optical and stabilitydata of further fluorinated Eu²⁺-doped strontium oxyorthosilicateluminophores.

Working Example C1

The working examples which follow relate to alkaline earth metalorthosilicate luminophores coated in accordance with exemplaryembodiments of the present invention and having a composition ofSr_(0.876)Ba_(1.024)SiO₄:Eu_(0.1). In the present exemplary embodiment,the base material is produced by a high-temperature solid-state reactionwherein the starting mixture comprises stoichiometric amounts of SrCO₃,BaCO₃, Eu₂O₃, SiO₂, and 0.2 mol of NH₄Cl.

The calcination process includes heating the crucible filled with thestarting mixture to 1275° C. in a nitrogen atmosphere, maintaining thistemperature over a period of 10 hours and subsequently cooling to roomtemperature. On attainment of the high-temperature ramp, 20% hydrogen isadded to the protective gas. After cooling, the resulting materials aresubjected to washing to remove flux residues, and then dried andscreened.

For fluorination of the base material, 150 g of the luminophore powderand 4.268 g of NH₄F are suspended in 3 L of H₂O and stirred over aperiod of 2 hours. After the coating procedure has ended, thefluorinated luminophore is filtered with suction to give sample F-401,washed with ethanol on the suction filter, and dried at 130° C. for 24hours. The optical data of sample F-401 are shown in Table 4, andF-401's emission spectrum is designated as “3” in FIG. 6 b. Table 4contains optical and stability data of fluorinated green-wavelengthemitting alkaline earth metal orthosilicate luminophores that haveadditionally been coated with SiO₂.

In a further step, the luminophore according to the present exemplaryembodiment in the form of sample F-401 may be provided with an SiO₂coating. For this purpose, 50 g of the fluorinatedSr_(0.876)Ba_(1.024)SiO₄:Eu_(0.1) luminophore powder are added to 500 mLof TEOS solution consisting of 1 L of ethanol, 25 g of TEOS and 150 mLof 32% aqueous ammonia, which has been prepared 24 hours before use.After a stirring time of 5 hours, reaction is terminated. Thesurface-coated luminophore in the form of sample F-401TS is filteredwith suction, washed with ethanol again, and dried. The optical data ofthe sample F-401TS are specified in Table 4, F-401TS's emission spectrumis designated as “4” in FIG. 6 b.

The emission spectra of the fluorinated luminophores of different matrixcomposition compared to the luminophores untreated in each case aredescribed in FIG. 1 a and FIG. 6 b, which show that the luminescenceintensities of the luminophores with fluorinated surface structureaccording to the exemplary embodiments of the present invention differslightly from those of the reference material. This is also confirmed bythe luminescence data of the luminophore samples according to exemplaryembodiments compiled in Table 1, Table 2, Table 3, Table 4, Table 5,Table 6, and Table 7 while somewhat lower luminescence intensities weremeasured in some cases for fluorinated and optionally additionally SiO₂coated samples. There are also examples in the tables referred to forsurface treatment leading to a slight increase in luminescenceefficiency. The latter effect may be attributed to the somewhat betteremission of light in the case of the coated materials.

In FIG. 7 a and FIG. 7 b, electron micrographs of a fluorinatedSr₃SiO₅:Eu luminophore according to exemplary embodiments of the presentinvention are compared to those of the untreated starting material.These micrographs demonstrate that the surface treatment, described inthe working examples, with suitable fluorinating agents leads to theformation of specific surface structures, which can be visualized withthe aid of scanning electron micrographs.

The situation is comparable for the electron micrographs shown in FIG. 8for green-wavelength light-emitting alkaline earth metal orthosilicateluminophores. The micrographs in FIG. 8 show the characteristic particlesurface of an untreated luminophore sample, that of the fluorinatedmaterial produced in accordance with the exemplary embodiments of thepresent invention, and that of a further sample derived from thestarting material, which had additionally been coated with SiO₂.

At the same time, it becomes clear from the results of correspondingenergy-dispersive X-ray spectroscopy (EDX) analyses shown in FIG. 9 thatthe surface structures contain fluorine. In addition to the peaks forstrontium (Sr), silicon (Si) and oxygen (O), which are characteristic ofthe luminophore matrix, pronounced singular reflections with significantpeak height are found in the EDX spectra of the luminophores fluorinatedin accordance with the invention, which must be assigned unambiguouslyto the element fluorine (F) on the basis of the peak's energy position.In addition, the spectrum shown also contains reflections designated asgold (Au) and palladium (Pd), which result from coating the luminophoresample with gold and palladium for reasons related to analysismethodology.

Further evidence for the fixing of finely dispersed fluorides or offluorine compounds or for the formation of networks of such compounds onthe surface of the luminophores according to exemplary embodiments ofthe present invention is documented in FIG. 10 and FIG. 11 by theresults of X-ray photoelectron spectroscopy (XPS) analyses. Fixing mayinclude adsorption and like means for chemisorption or physisorption.The XPS spectrum, shown in FIG. 10, of a luminophore of base latticecomposition Sr_(2.9)Ba_(0.01)Ca_(0.05)Eu_(0.04)SiO₅ treated with NH₄Faccording to Working Example 1 shows that it is also possible with thissolid-state analysis method to detect the element fluorine (F) as aconstituent of the surface structures of the fluorinated luminophores.Further conclusions may also be drawn from the XPS spectrum. Forexample, it is evident from the comparison of the internally calibratedXPS spectra of the NH₄F-fluorinated oxyorthosilicate luminophore (curve2 in FIG. 11) with that of a sample of a mechanical mixture of thecorresponding luminophore matrix with an equivalent amount of NH₄F(curve 1 of FIG. 11) that the F 1s peaks determined in each case havedifferent intensities and also exhibit a shift in binding energyrelative to one another as shown in FIG. 11.

The lower intensity of the F 1s peak of the sample labeled as curve 2can be interpreted as loss of some of the added fluorine from theluminophore surface during processing. The shift in the F is peak tolower binding energies of curve 1 may indicate formation of a chemicalbond between the applied fluorinating agent and the surface of theluminophore matrix.

In Table 1, Table 2, Table 3, Table 4, Table 5, and Table 6, severalluminescence parameters of different silicatic luminophores configuredin accordance with exemplary embodiments of the present invention andthe results of the stability tests are compiled and compared with thoseof the unchanged (i.e., non-fluorinated surface) luminophore powders andin some cases with those of commercial comparative luminophores. Table 5contains optical and stability data of fluorinated and of fluorinatedand SiO₂-coated Eu²⁺-coated strontium oxyorthosilicate luminophores.Table 6 contains optical and stability data of SiO₂-coated strontiumoxyorthosilicate luminophores that have been fluorinated.

The moisture stability of the materials was assessed by storage of thecorresponding luminophore samples in a climate-controlled cabinet, whichwas operated at a temperature of 85° C. and 85% air humidity, for sevendays. Subsequently, the luminophores were dried at 150° C. for 24 hoursand then subjected to a comparative measurement of the luminescenceyield. The results of the comparative luminescence measurementsdemonstrate that both the luminescence efficiencies of the luminophoresaccording to exemplary embodiments of the present invention and thetemperature dependencies thereof are equal to those of commercialeuropium-activated alkaline earth metal oxyorthosilicate orcorresponding orthosilicate luminophores, or even exceed them. Secondly,the results of the stability tests show that the luminophores accordingto exemplary embodiments of the present invention with fluorinatedsurface structure and optional additional SiO₂ coating, as shown inTable 4, Table 5, and Table 6, have significantly improved moistureresistances compared to unchanged (i.e. non-fluorinated surface)luminophores of the same matrix composition.

As discussed above, silicate luminophores are surface modified with acoating including a fluorinated coating. The fluorinated coating canalso be applied to quantum dot luminophores. Semiconductor quantum dotluminophores convert high energy radiation into visible light, based ontheir band gap structure. In addition, quantum dot luminophores are veryreactive due to their small size, and thus, quantum dots have also acomparatively low radiation stability and high sensitivity to water, airhumidity, and other environmental factors.

FIG. 12 and FIG. 13 depict sectional views of surface modified quantumdot (QD) luminophores 30 and 30 a, according to exemplary embodiments ofthe present invention.

Referring to FIG. 12, the surface modified QD luminophore 30 comprises aQD luminophore 11 and a coating disposed on the surface of the QDluminophore 11. The coating may comprise a moisture barrier layer 13 anda fluorinated coating 15.

The QD luminophore 11 comprises a II-VI or III-V group compoundsemiconductor QD luminophore. The II-VI group compound semiconductor QDluminophore may comprise CdSe or CdS, and the III-V group compoundsemiconductor QD luminophore may comprise AlInGaP, AlInGaAs, or AlInGaN,but the invention is not limited thereto.

The moisture barrier layer 13 may comprise an inorganic material of MgO,Al₂O₃, Y₂O₃, La₂O₃, Gd₂O₃, Lu₂O₃, and SiO₂, the correspondingprecursors, and/or at least one semiconductor material having a bandgapwider than that of the QD luminophore, and/or an organic ligand of anamine, an acid or SH. The moisture barrier layer 13 may be a singlelayer or multi-layers.

The inorganic materials are similar to the inorganic materials discussedin the previous embodiments, and detailed descriptions thereof areomitted. The moisture barrier layer 13 including the semiconductormaterial may be a shell surrounding the QD luminophore 11. Thesemiconductor material has a lattice mismatch with the QD luminophore11. The larger the lattice mismatch therebetween, the higher theconversion efficiency of the surface modified luminophore 30. A bufferlayer 12 may be applied between the QD luminophore 11 and thesemiconductor layer 13, as shown in FIG. 13. In the case of CdS or CdSeQD luminophores, the semiconductor material may be, for example, ZnS,and the buffer layer 12 may be ZnCdS or ZnCdSe. The moisture barrierlayer 13 may also be formed to have the semiconductor material and theorganic ligand of an amine, an acid or SH.

The fluorinated coating 15 is similar to the fluorinated coatingdescribed above in the previous embodiments. The fluorinated coating 15may comprise a fluorinated inorganic agent, a fluorinated organic agent,or a combination of a fluorinated inorganic agent and a fluorinatedorganic agent. The fluorinated coating generates hydrophobic surfacesites.

The fluorinated coating 15 may comprise a surface fixed or cross-linkedfluorine, or fluorine compounds. An optional additional coating 16including non-fluorinated layer-forming materials can be applied to thefluorinated coating 15, as shown in FIG. 13.

According to exemplary embodiments of the present invention, the QDluminophores may be fluorinated using fluorine-functionalizedorganosilanes having the formula Si(OR)₃X, where R is CH₃, C₂H₅, . . . ,and X is a F-functionalized organic ligand. Controlled hydrolysis andcondensation may achieve the formation of a fluorinated barrier layer ona QD luminophore matrix, which may be a barrier and may also havehydrophobic properties. In addition, the semiconductor layer 13 may beformed on the QD luminophore 11 before forming the fluorinated barrierlayer thereon.

The fluorination of the surfaces of the QD luminophores is similar tothe fluorination of the surfaces of the pulverulent alkaline earth metalsilicate luminophores. However, the moisture barrier layer 13 may beformed before the fluorination of the surfaces of the QD luminophores,in order to prevent surface reactions of the QD luminophores.

It will be apparent to those skilled in the art that variousmodifications and variation can be made in the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

TABLE 1 Intensity after Half- Intensity climate- Color height at 150° C.controlled Composition of the Sample Fluorinating Proportion Intensitycoordinates width I₁₅₀/I₂₅ chamber test luminophore matrix No. agent [%]L [%] x y [nm] [%] I_(before)/I_(after) [%] Sr₃SiO₅:Eu commercial 97.60.5420 0.4560 68.8 91.3 71.7 Sr_(2.9)Ba_(0.01)Ca_(0.05)Eu_(0.04)SiO₅Starting material for 100 0.5462 0.4518 71.0 92.7 92.3 fluorinationtests F-100 NH₄F 2.5 99.1 0.5459 0.4522 70.6 92.4 93.4 F-101 NH₄F 5F-102 NH₄F 7.5 F-103 NH₄F 10 additionally heat-treated samples (1 hour,400° C., 35% H₂) F-100T NH₄F 2.5 97.3 0.5457 0.4524 70.7 92.1 93.1F-101T NH₄F 5 98.3 0.5453 0.4527 70.9 92.8 94.7 F-102T NH₄F 7.5 97.20.5454 0.4525 71.1 92.3 103.7 F-103T NH₄F 10 98.3 0.5456 0.4525 70.992.7 102.3

TABLE 2 Intensity after Half- Intensity climate- Color height at 150° C.controlled Composition of the Sample Proportion Intensity coordinateswidth I₁₅₀/I₂₅ chamber test luminophore matrix No. Fluorinating agent[%] L [%] x y [nm] [%] I_(before)/I_(after) [%] Sr₃SiO₅:Eu commercial97.6 0.5420 0.4560 68.8 91.3 71.7Sr_(2.9)Ba_(0.01)Ca_(0.05)Eu_(0.04)SiO₅ Starting material for 100 0.54620.4518 71.0 92.7 92.3 fluorination tests F-200 NH₄HF₂ 2.5 98.8 0.54590.4521 70.6 93.1 93.4 F-201 NH₄HF₂ 5 99.2 0.5455 0.4525 70.9 92.6 94.9F-202 NH₄HF₂ 7.5 99.4 0.5459 0.4521 70.8 91.9 98.7 F-203 NH₄HF₂ 10 98.80.5457 0.4522 70.9 92.3 98.9 additionally heat-treated samples (1 h,400° C., 35% H₂) F-200T NH₄HF₂ 2.5 97.3 0.5458 0.4523 70.6 92.7 103.3F-201T NH₄HF₂ 5 98.3 0.5456 0.4525 71.1 92.1 102.6 F-202T NH₄HF₂ 7.597.2 0.5454 0.4520 71.1 92.1 102.7 F-203T NH₄HF₂ 10 98.3 0.5455 0.452670.9 92.5 102.0

TABLE 3 Intensity after Color climate-controlled Composition of theSample Fluorinating Proportion Intensity coordinates chamber testluminophore matrix No. agent [%] L [%] x y I_(before)/I_(after) [%]Sr₃SiO₅:Eu commercial 97.6 0.5420 0.4560 71.7Sr_(2.9485)Ba_(0.01)Cu_(0.0015)Eu_(0.04)SiO₅ Starting material for 10083.6 fluorination tests F-300 LiF 5 99.1 0.5373 0.4604 93.3 F-301 + 1098.5 0.5381 0.4598 91.9 F-310 BaF₂ 1 97.8 0.5374 0.4598 93.6 F-311 + 598.2 0.5380 0.4521 89.0 F-320 AlF₃ 5 98.8 0.5371 0.4606 99.2 F-321 + 1098.2 0.5407 0.4572 94.2 additionally heat-treated samples (1 h, 400° C.,35% H₂) F-300T LiF 5 99.0 0.5372 0.4505 95.1 F-310T BaF₂ 1 98.0 0.53710.4607 95.7 F-320T AlF₃ 5 99.1 0.5368 0.4608 99.4

TABLE 4 Intensity after climate- Color controlled Composition of theSample Proportion Intensity coordinates chamber test luminophore matrixNo. Fluorination [%] Coating L [%] x y I_(before)/I_(after) [%]Sr_(0.876)Ba_(1.024)Eu_(0.1)SiO₄ Starting material for 100 0.2943 0.629883.6 fluorination tests F-400 NH₄F 10 — 99.5 0.2938 0.6300 97.9 F-400TSNH₄F 10 TEOS 99.1 0.2933 0.6294 98.9 F-401 NH₄F 20 — 99.8 0.2942 0.629796.6 F-401TS NH₄F 20 TEOS 100.7 0.2935 0.6298 98.7 F-402 NH₄FHF₂ 10 —99.2 0.2938 0.6299 98.2 F-402TS NH₄FHF₂ 10 TEOS 100.4 0.2932 0.6302 99.5F-403 NH₄FHF₂ 20 — 100.0 0.2941 0.6302 99.7 F-403TS NH₄FHF₂ 20 TEOS101.4 0.2940 0.6307 100.1

TABLE 5 Intensity after climate-controlled Luminophore Sample ProportionIntensity Color coordinates chamber test composition No. Fluorination[%] Coating L [%] x y I_(before)/I_(after) [%]Sr_(2.935)Ba_(0.015)Eu_(0.05)SiO₅ 98.2 0.5422 0.4565 72.3 100 0.53860.4592 78.4 F-500 NH₄F 10 — 98.0 0.5383 0.4594 91.6 F-500TS NH₄F 10 TEOS93.9 0.5372 0.4604 101.1 F-501 NH₄F 20 — 97.2 0.5382 0.4594 97.1 F-501TSNH₄F 20 TEOS 93.3 0.5372 0.4605 101.5 F-502 NH₄HF₂ 10 — 97.8 0.53870.4591 97.3 F-502TS NH₄HF₂ 10 TEOS 93.2 0.5374 0.4601 101.8 F-503 NH₄HF₂20 — 95.1 0.5383 0.4595 99.5 F-503TS NH₄HF₂ 20 TEOS 93.0 0.5376 0.4699100.7

TABLE 6 Intensity after climate-controlled Luminophore Sample ProportionIntensity Color coordinates chamber test composition No. CoatingFluorination [%] L [%] x y I_(before)/I_(after) [%] Sr₃SiO₅:Eucommercial 98.3 0.5319 0.4563 69.3Sr_(2.948)Ba_(0.01)Cu_(0.002)Eu_(0.04)SiO₅ Original 100 0.5462 0.451492.0 TS-600 TEOS — 101.7 0.5465 0.4515 96.8 F-TS-600 TEOS NH₄F 20 100.60.5458 0.4522 102.7 TS-601 TEOS — 98.5 0.5456 0.4523 98.4 F-TS-601 TEOSNH₄F 20 97.6 0.5452 0.4528 103.4

What is claimed is:
 1. A light emitting device, comprising: a firstlight emitting diode; and a surface-modified luminophore configured toabsorb light emitted from the first light emitting diode and configuredto emit light having a different wavelength from the absorbed light, thesurface-modified luminophore comprising: a quantum dot (QD) luminophore;and a fluorinated coating disposed on the QD luminophore.
 2. The lightemitting device of claim 1, wherein the fluorinated coating isconfigured to generate hydrophobic surface sites, the fluorinatedcoating comprising a fluorinated inorganic agent, a fluorinated organicagent, or both the fluorinated inorganic agent and the fluorinatedorganic agent.
 3. The light emitting device of claim 1, wherein thesurface-modified luminophore further comprises a moisture barrier layercomprising an oxide disposed on the fluorinated coating or disposedbetween the fluorinated coating and the QD luminophore.
 4. The lightemitting device of claim 3, wherein the oxide comprises at least one ofMgO, Al₂O₃, Y₂O₃, La₂O₃, Gd₂O₃, Lu₂O₃, and SiO₂.
 5. The light emittingdevice of claim 1, wherein: the QD luminophore comprises a II-VI groupcompound semiconductor or a III-V group compound semiconductor; and thefluorinated coating comprises a fluorinated barrier layer formed byfluorinating the QD luminophore using a fluorine-functionalizedorganosilane comprising the general formula Si(OR)₃X, where R is analkyl group, and X is a fluorine-functionalized organic ligand.
 6. Thelight emitting device of claim 1, wherein the fluorinated coatingcomprises a surface fixed or cross-linked fluorine or fluorine compound.7. The light emitting device of claim 6, wherein the surface-modifiedluminophore further comprises a non-fluorinated layer disposed on thefluorinated coating.
 8. The light emitting device of claim 1, whereinthe surface-modified luminophore further comprises a moisture barrierlayer disposed between the QD luminophore and the fluorinated coating,the moisture barrier layer comprising at least one of: at least oneinorganic material selected from MgO, Al₂O₃, Y₂O₃, La₂O₃, Gd₂O₃, Lu₂O₃,SiO₂, and corresponding precursors thereof; at least one semiconductormaterial having a bandgap wider than that of the QD luminophore; and atleast one of an organic ligand of an amine, an acid, or SH.
 9. The lightemitting device of claim 7, wherein the at least one semiconductormaterial has a lattice mismatch with the QD luminophore and surroundsthe QD luminophore.
 10. The light emitting device of claim 1, whereinthe first light emitting diode and the luminophore are combined in apackage.
 11. The light emitting device of claim 10, further comprising:a second light emitting diode in the package, wherein the second lightemitting diode is configured to emit light having a longer emission peakwavelength than that of the luminophore.
 12. The light emitting deviceof claim 10, wherein the package further comprises a substrate on whichthe first light emitting diode is mounted.
 13. The light emitting deviceof claim 12, wherein the substrate comprises a printed circuit board ora lead frame.
 14. The light emitting device of claim 13, furthercomprising a molding member encapsulating the first light emittingdiode, wherein the surface-modified luminophore is arranged within themolding member.
 15. The light emitting device of claim 10, wherein thepackage comprises a heat sink on which the first light emitting diode ismounted.
 16. The light emitting device of claim 1, wherein the firstlight emitting diode comprises a plurality of light emitting cells.